<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="51c8f867-9fa0-4ca8-a82f-0f76d06d3bc2" />
  <url value="https://fhir.nhs.uk/StructureDefinition/Extension-DM-ControlledDrug" />
  <name value="ExtensionDMControlledDrug" />
  <status value="draft" />
  <fhirVersion value="4.0.1" />
  <mapping>
    <identity value="rim" />
    <uri value="http://hl7.org/v3" />
    <name value="RIM Mapping" />
  </mapping>
  <kind value="complex-type" />
  <abstract value="false" />
  <context>
    <type value="element" />
    <expression value="MedicationRequest" />
  </context>
  <type value="Extension" />
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Extension" />
  <derivation value="constraint" />
  <differential>
    <element id="Extension">
      <path value="Extension" />
      <constraint>
        <key value="eps-cd1" />
        <severity value="error" />
        <human value="Extension(controlledDrug) - For schedule 2 or 3 Controlled Drugs, the quantity must be expressed in words" />
        <expression value="(((extension('schedule').value.code='CD2' and extension('quantityWords').exists()) or (extension('schedule').value.code='CD3' and extension('quantityWords').exists()) or (extension('schedule').value.code != 'CD2' and extension('schedule').value.code != 'CD3')) and extension('scheduled').exists()) or (extension('scheduled').exists().not())" />
      </constraint>
    </element>
    <element id="Extension.extension">
      <path value="Extension.extension" />
      <slicing>
        <discriminator>
          <type value="value" />
          <path value="url" />
        </discriminator>
        <rules value="open" />
      </slicing>
      <min value="0" />
    </element>
    <element id="Extension.extension:quantityWords">
      <path value="Extension.extension" />
      <sliceName value="quantityWords" />
      <min value="0" />
      <max value="1" />
    </element>
    <element id="Extension.extension:quantityWords.url">
      <path value="Extension.extension.url" />
      <fixedUri value="quantityWords" />
    </element>
    <element id="Extension.extension:quantityWords.value[x]">
      <path value="Extension.extension.value[x]" />
      <min value="1" />
      <type>
        <code value="string" />
      </type>
    </element>
    <element id="Extension.extension:schedule">
      <path value="Extension.extension" />
      <sliceName value="schedule" />
      <min value="0" />
      <max value="1" />
      <binding>
        <strength value="required" />
        <valueSet value="https://fhir.nhs.uk/ValueSet/DM-medicationrequest-controlled-drug" />
      </binding>
    </element>
    <element id="Extension.extension:schedule.url">
      <path value="Extension.extension.url" />
      <fixedUri value="schedule" />
    </element>
    <element id="Extension.extension:schedule.value[x]">
      <path value="Extension.extension.value[x]" />
      <min value="1" />
      <type>
        <code value="Coding" />
      </type>
    </element>
    <element id="Extension.extension:schedule.value[x].system">
      <path value="Extension.extension.value[x].system" />
      <min value="1" />
    </element>
    <element id="Extension.extension:schedule.value[x].code">
      <path value="Extension.extension.value[x].code" />
      <min value="1" />
    </element>
    <element id="Extension.extension:schedule.value[x].display">
      <path value="Extension.extension.value[x].display" />
      <min value="1" />
    </element>
    <element id="Extension.url">
      <path value="Extension.url" />
      <fixedUri value="https://fhir.nhs.uk/StructureDefinition/Extension-DM-ControlledDrug" />
    </element>
    <element id="Extension.value[x]">
      <path value="Extension.value[x]" />
      <max value="0" />
    </element>
  </differential>
</StructureDefinition>